The CBN is a material having the highest hardness after diamond. Since the CBN has low reactivity with respect to metal, its sintered compact is used for cutting a heat-resistant alloy or quenched steel. In the CBN sintered compact having such high hardness also, if it is coated with a film, there is effect that a cutting edge is prevented from being worn. A cutting edge portion of the coating film is rounded, and as the thickness of the coating film is increased, this portion becomes rounder. Patent Document 1 discloses a coated CBN sintered compact having a wear-resistant layer, an intermediate layer and an outermost layer on the CBN sintered compact. There is provided a surface-coated high hardness material for a tool coated with TiAl (CNO) and the like as the wear-resistant layer, and with TiN and the like as the intermediate layer or the outermost layer.
Patent Document 2 discloses that a CBN sintered compact includes a coating film such as composite nitride and composite nitrogen carbide including titanium and aluminum. Especially, in a composite hard film coated member, a ratio of X-ray diffraction strength of crystal plane (200) of the coating film and X-ray diffraction strength of crystal plane (111) of the coating film falls in a specific range, and thickness of the coating film is 1 to 15 μm.
Patent Document 1: Japanese Patent Application Laid-open No. H8-119774, Pages 2 and 6 to 10, Tables 1, 3, 5
Patent Document 2: Japanese Patent Application Laid-open No. 2001-234328, Page 2